Latching mechanism for access door

ABSTRACT

An enclosed structure having an opening for access thereto with an acesss door, which can close the opening, mounted movably to the structure, and a latch mechanism for securing the door in closed position over the opening in the structure. The latch mechanism comprises a locking bolt pivotally mounted to a supporting bracket on the structure to be swung into and out of engagement with a pair of mating troughs in the edge of the door and opening. A pivot shaft extends laterally from the side of the bolt between the bolt ends and a cam is mounted on the pivot shaft to rotate relative to the bolt. A lever arm is joined to the cam to rotate the cam. The cam has a face which contacts the opening edge, restrains forward movement of the bolt and applies a rearward force thereon.

United States Patent 1191 Stubert 1 Mar. 27, 1973 [54] LATCHING MECHANISM FOR ACCESS 2,926,037 2/1960 Granzow ..292 113 DOOR Primary Exdminer-Richard E. Moore [75] Inventor 111 Wesley stuben Memphis Attorney-Merriam, Marshall, Shapiro & Klose [73] Assignee: Chicago Bridge & Iron Company, ABSTRACT Oak Brook An enclosed structure having an opening for access 22 l d; Man 24 1971 thereto with an acesss door, which can close the opening, mounted movably to the structure, and a latch [21] PP N05 1271231 mechanism for securing the door in closed position over the opening in the structure. The latch 52 11.5, c1, ..292/64, 292/256.75, 292/010. 49 mechanism comprises a loc"mg Pivmany 51 Int. Cl. E051; mmmed a suppmting bracket the structure to [58] Field of Search....292/64 65 66 110 111 113 be swung mm and engagement with a Pair Of 292/256 mating troughs in the edge of the door and opening. A pivot shaft extends laterally from the side of the bolt 56 R f C} d between the bolt ends and a cam is mounted on the l e erences l e pivot shaft to rotate relative to the bolt. A lever arm is UNITED STATES PATENTS joined to the cam to rotate the cam. The cam has 3.

face which contacts the opening edge, restrains for- 2,632,663 3/1953 Croft ..292/11] ward movement of the bolt and applies a rearward l Eckerle ...292/66 X force thereo 3,229,791 1/1966 Soman ..292/65 X 2,834,504 5/1958 Annicg ..292/256.75 X 29 Claims, 15 Drawing Figures 5 /V 50-5 1 t 5 2 "\Q i 1 3a 1 o 28 n W I /I2 I Io 4e 35 39 Patented March 27, 1973 4 Sheets-Sheet 1 V//// //////Al h\ \NN\NNM INVENTOR.

ATTORNEYS.

LATCIIING MECHANISM FOR ACCESS DOOR This invention relates to structures having openings for access thereto and to doors for closing and sealing such openings as well as latching or locking mechanisms used to secure such doors in place to effectively close ,an access opening in such structures.

There are many structures including buildings, vessels, vaults and tanks to which access must be obtained periodically. For safety and security reasons, and sometimes for normal use of the structure, a door must be provided which is sufficiently strong, although reasonably movable, to seal off an access opening to the structure yet permit access to the structure within a reasonably short time. Although access doors of such general type are often mounted on hinge means so that they may be swung in and out to close and open the access opening, there is generally a need for additional means to tightly seal and secure the door around and about the access opening side edges. Latching mechanisms of various types and intricacies have been employed to keep an access door closed and sealed. While there are such locking and latching mechanisms available, there is a need for an improved latching mechanism which will be suitable for tightly securing an access door to an opening in a structure. The subject invention provides such a latching mechanism and one which is highly useful in combination with an access door and access opening.

According to the present invention, there is provided a latch mechanism having a locking bolt pivotally mounted to a supporting bracket and with a pivot shaft extending laterally from the side of the bolt between the bolt ends. The pivot shaft has a cam mounted thereon so that the cam and bolt can rotate relative to one another. A lever arm is joined to the cam, advisably at a location below the body of the bolt. When the lever arm is pulled, it causes the cam to rotate a predetermined distance which is limited by a restraining means. Continued pulling one the lever arm causes the bolt to be moved because the restraining means bars further rotation of the cam. The restraining means can comprise a pin, joined to the cam, which extends below the bolt. When thelever arm is pulled and the cam rotates, the pin moves up against the bolt and restrains further rotation of the cam. Further pulling on the lever arm produces a lifting or displacement action applied against the body ofthe bolt by the pin. Continued movement of the bolt in this manner causes the bolt to be displaced from the nesting and locking position in a pair of adjacent mated troughs which are located in the edge portions of an access door and an access opening of a structure. A restraining means is located on the bolt on the front side of the edge portion of the door and the rear side of the edge portion of the structure around the opening to force such edge portions together to thereby achieve a tight seal. A resilient means is advisably used in operable direct or indirect action on the bolt to hold the bolt in position in the troughs at the edge portions of the door and access opening. This can be a suitable spring joined from the cam and to the structure close to the access opening or a spring extending from the bolt rearward end to the structure.

Although the bolt can be simply pivotally mounted to the supporting bracket, it is advisably joined thereto by a pivotable unit which also permits the bolt to slide forwardly and backwardly an yet permit pivotable movement of the bolt. When such slidable action of the bolt about the pivot is employed, it is also desirable that the mechanism have a resilient means, such as a spring, which urges the bolt forward with respect to the bracket. This aids in freeing the front end of the bolt from the door face. In addition, the cam should have a contact face which, upon touching a stationary surface on the structure, restrains or prevents further forward displacement of the bolt. Such contact surface is also advisably one which comes into contact with a stop lug on a stationary surface of the structure to restrict or stop pivotable movement of the bolt away from the locking trough on the door and structure.

The latching mechanism of this invention can be used for any clamping, locking or securing operation that may require initial preset adjustment and quick release or clamping to a self-locking condition. The linear movement of the bolt permits greater latitude in positioning it and allows the use of resilient materials for sealing or for protecting mating surfaces of delicate parts. With the use of resilient materials at the mating surfaces, the latching or-clamping force to lock the device may be kept low and yet the bolt, cam arms and rollers can be sized to take subsequent high loads in the self-locking position. Another feature of the invention is the ability of the bolt to move out of the way to permit a work piece, door or other secured component to be easily removed without disassembly or further work.

This invention will be described further in conjunction with the attached drawingsin which:

' FIG. 1 is a plan view, partly broken away, of one embodiment ofa latching mechanism, provided by this invention, shown mounted on a structure having an access opening whichcan be closed by a door secured and locked in place by the latching mechanism;

FIG. 2 is a side elevational view, partly in section, showing the latching mechanism of FIG. 1 in combination with portions of an access opening and an access door;

FIG. 3 is similar to FIG. 2 except that the latching mechanism is shown in a partially released position;

FIG. 4 illustrates the latching device of FIGS. 1 to 3 but with the latching mechanism in an open or unlocked position;

FIG. 5 is a front view of the latching mechanism of FIGS. 1 to 4 shown in combination with the edge of a circular access door and circular access opening in a structure;

FIG. 6 is a plan view, partly in section, of the locking bolt used in the latching mechanism shown in FIGS. 1 to 5;

. FIG. 7 is a side elevational view of the locking bolt of FIG. 6;

FIG. 8 is a plan view showing one of the cams, of the latching mechanism of FIGS. 1 to 5, having a roller mounted thereon;

FIG. 9 is a side elevational view of the cam of FIG. 8;

FIG. 10 is a plan or top view, partly broken away, of another embodiment of a latching mechanism provided by this invention;

FIG. 11 is a side elevational view of the latching mechanism of FIG. 10 in locked position;

FIG. 12 is a side elevational view of the latching mechanism of FIGS. 10 and 11 in released position;

FIG. 13 is a side elevational view of the latching mechanism of FIGS. to 12 in unlocked position;

FIG. 14 is a front view of the latching mechanism of FIGS. 10 and 11 in locked position; and

FIG. is a side elevational view, partlybroken away, showing the bolt and bracket pivot structure.

So far as is practical, the various parts or elements which are the same in .the different views of the to-face contact with the front surface of flange 11 to close the access opening.

The edge portion of flange 11 and the edge portion 13 of the door are provided with a series of troughs 14 as shown in FIG. 5. The troughs 14 have spaced apart parallel walls and ahemicircular bottom portion in which the locking bolt 15 nests in order to secure the door in place. The edge portion of the door, and the edge portion of the structure, advisably have a plurality of such troughs spaced apart around the door and opening so that a plurality of locking bolts can secure the door tightly in place. Each trough on the door is located to mate with a trough on the structure to constitute a pair of troughs in which an anchor bolt of the latching mechanism nests. Thus, when bolt 15 is in locking position, it nests in a pair of troughs in aligned mating position.

Locking bolt 15 is providedwith an elongated opening 16 at the pivot or back end. Pivot pin 17 extends through opening 16 and has its opposing ends secured into suitable openings located in bracket arms 18 and 19. Bracket arms 18 and 19 are joined at their bottom and thus are part of a single piece, although they can be separate pieces. The bracket arms 18 and 19 are joined, such as by welding, to wall 10.

Axially positioned hole 20 is located in the pivotal end of locking bolt 15. Hole 20 provides a space for compression spring 21. One end of compression spring 21 presses against the bottom of hole 20 and the other end of the spring presses against pivot pin 17. As a result of compression spring 21 and the elongated shape of hole 16, anchor bolt 15 can be displaced forward and backward to a limited extent and'still be pivoted. I

Anchor bolt 15 has a major portion 22 which is essentially rectangular or square in cross-section except for a more or less centrally located section 23 which is enlarged in order to provide for a lateral hole 24 therein. The forward end 25 of anchor bolt 15, and particularly that part which fits in the troughs, is circular in cross-section and is threaded at its end to receive the pair of nuts 26. Shaft 27 is rotatably positioned in hole 24 in anchor bolt 15 and the ends of pivot shaft 27 extend outwardly from the sides of the anchor bolt. Cam 28 is fixedly placed on one end of pivot shaft 27 and cam 29 is fixedly placed on the other end of pivot shaft 27. Cams 28 and 29 are mirror images of each other. Cam 28 is secured in place on the end of shaft 27 by a key 30 so that the cam and shaft rotate in unison. A

similar key is used to hold cam 29 and shaft 27 for the same reason. Both cams and the shaft thus must move or rotate simultaneously. Roller 31 is secured on cam 28 by a bolt 32. Roller 33 is secured on cam 29 by bolt 34. Rollers 31 and 33 are identical and are positioned in identical positions on each of their respective cams.

Pin 35 is positioned at one end in hole 36 in cam 28 and at the other end in a similar hole in cam 29. Pin 35 is located below anchor bolt 15.

Tab 37 mounted on cam 28 provides a means on which to hook the upper end of tension spring 38. The lower end of spring 38 is hooked onto a pin 39 secured to wall 10. Similarly tension spring 40 is hooked at one end to tab 41 on cam 29 and at the other end to a pin 42 mounted on wall 10. Lever arm 45 is joined to cam 28 by a pivot pin 46 set'in hole 43 in the cam. The springs serve to urge anchor bolt 15 into the troughs provided in the edge portions of the door and access opening as shown in FIG. 3 upon initial extension of lever arm 45. This assures seating of the bolt prior to its retraction and locking. Springs 38 and 40 are required only when the mechanism is mounted in a position other than horizontal, or if it is deemed advisable to have more return force to position the bolt in the troughs.

Lever arm 45 is operably connected to a piston positioned in hydraulic cylinder 47. The piston is caused to move in either direction by means of a fluid fed to either side thereof by hydraulic fluid lines 48 and 49.

The end of hydraulic cylinder 47 is pivotally mounted 1 by pin 50 to a support tab 51. Plate 52extends from wall 10 and tab 51 is joined thereto and to laterally extending plate 53. Angled sheet 54 extends forward from plate 53 to partially in front of the latching mechanism and provides a safety shield.

A pair of stops 60 and 61 are bolted onto the outer edge of flange 11 on the side of the trough in the edge portion of the structure. Stops 60 and 61 are provided to restrain rollers 31 and 33 against unlimited upward movement during the removal of anchor bolt 15 from the troughs in which it nests for locking the access door to close the opening. The stops also act with the rollers to effect a self-locking action when the bolt is in locking position. I

FIG. 2 shows the latching mechanism in position to lock the access door against the edge portion of the access opening. When lever arm 45 is forced downwardly by hydraulic cylinder 47, it causes cam 28 to rotate counterclockwise when viewed from the position shown in FIG. 2. This action causes anchor bolt 15 to become nested in the respective troughs in the edge portion of the door and flange 11 and urges rollers 31 and 33 into contact with the rear surface of flange 11. The rollers will be in overcenter position relative to the shaft 27 so that a self-locking action is achieved.

As shown in FIG. 3,-upward movement .of lever arm 45 by means of hydraulic cylinder 47 causes cam 28, and simultaneously cam 29, to rotate clockwise when viewed from the position shown in FIG. 3. This rotation removes rollers 31 and 33 from contact with the back of flange l1 and permits the spring 21 to shift or move anchor bolt 15 to the right to release the inner nut of nuts 26 from contact with the front face of the edge portion 13 of the access door. With the nut so released from the front of the door, continued upward movement of lever arm 45 results in further rotation of the cams 28 and 29. This rotation of the cams brings pin 35 into contact with the lower wall of anchor bolt so that upon further upward action of lever arm 45 there is a positive movement or lifting of anchor bolt 15 from its nesting position in the troughs in the edge of the door and the access opening. The pivotal movement of anchor bolt 15 about pivot .pin 17 raises the bolt in a counterclockwise manner, as shown in FIG. 4, to a position at which it is completely clear of the respective troughs in the edge portions of the access door andthe access opening in the structure. B"y reversing the described operation, anchor bolt 15 can be repositioned into locking arrangement to secure the door tightly in place against the wall surface face of the access opening.

The latching mechanism of this invention is relatively inexpensive to construct and by setting the hydraulic cylinders of each anchor bolt to operate in parallel arrangement all of the anchor bolts used to secure an access door in closed position can be opened by one automatic operation. Release of nuts 26 is not essential for such operation sincethe action of the lever arm 45 causes the rollers 31 and 33 from remaining in contact with the back face of flange 11. Once such rollers are removed from contact with flange 11, anchor bolt 15 is released and the seal thereby loosened.

It is not considered an essential requirement of this invention to usetwo earns 28 and 29. A single cam arrangement could be used satisfactorily. Similarly compression spring 21 could be eliminated although its use is considered advisable. Of course, other resilient means besides springs can be used to achieve the described action and forces desired for suitable operation of the latching mechanism.

Lever arm 45 need not be operated by hydraulic means in all instances since manual operation of the lever is highly feasible in some instances, particularly when resilient materials are used as a seal at the mating surfaces.

Another embodiment of the latching mechanism of this invention is shown in FIGS. 10 to 15.

As shown in FIGS. 10 to 15, wall 70 constitutes the periphery of an access opening and it has a lateral flange 71. Gaskets 72 are positioned in grooves in'the face of flange 71. Edge portion 73 of an access door spans an access opening and is positioned to contact the front surface of flange 71 to close the opening.

The edge offlange 71 and the edge 73 of the door are provided with a series of troughs 74. Troughs 74 have spaced apart parallel walls and a hemicircular bottom they can be separate pieces. The bracket arms 78 are I joined by welding to wall 70. As a result of compression in which the locking bolt nests to secure the door in place. The edge portion of the door, and the edge portion of the structure, can have one or more of such troughs spaced apart around the door and opening so that one or more locking bolts can secure the door tightly in place.

A threaded midsection 80 (FIG. 15) of bolt 75 has a nut 81 threaded thereon followed by compression spring 82, which slips over the threaded portion, and washer 83. Washer 83 presses against pin 84 which runs through laterally located elongated hole 85 (FIG. 15) in bolt 75. The ends of pin 84 are secured in a pair of bracket arms 78. Bracket arms 78 are joined at their bottom and thus are part of a single piece, although spring 82 and the elongated shape of hole 85, anchor bolt 75 can be displaced forward and backward to a limited extent and still be pivoted.

Anchor bolt 75 has a more or less centrally located section 93 which is enlarged in order to provide for a lateral hole therein. The forward end of anchor bolt 75, and particularly that part which fits in the troughs, is circular in cross-section and is threaded at its end to receive the pair of nuts 96. Shaft 97 is rotatably positioned in the hole in anchor bolt 75 and the ends of shaft 97 extend outwardly from the sides of the anchor bolt. Cam 98 is fixedly placed on one end of shaft 97 and cam 99 is fixedly placed on the other end of shaft 97. Cams 98 and 99 are mirror images of each other. Cam 98 is secured in place on the end of shaft 97 by a key 100 so that the cam and shaft rotate in unison. A similar key is used to hold cam 99 and shaft 97 for the same reason. Both cams and the shaft thus must move or rotate simultaneously. Roller 101 is rotatably secured on cam 98 by a bolt 102. Roller 103 is rotatably secured on cam 99 by bolt 104. Rollers 101 and 103 are identical and are positioned in identical positions on each of their respective cams.

Lever arm is operably connected to a piston positioned in hydraulic cylinder 117. The piston is caused to move in either direction by means of a fluid fed to either side thereof by hydraulic fluid lines 118 and 119. The end of hydraulic cylinder 117 is pivotally mounted by pin 120 to a support tab 121. Plate 122 extends from wall 70 and tab 121 is joined thereto and to laterally extending plate 123. Sheet 124 extends forward from plate 123 to partially in front of the latching mechanism and provides a safety shield.

Yoke 125 is mounted on the end of lever arm 115. Yoke 125 has a cross-arm 126 and downwardly extending fingers 127 and 128 therefrom. Finger 127 is rotatably joined to cam 98, and finger 128 is rotatably joined to cam 99, by a pin 129 which extends beneath bolt 75.

A pair of stops 130 and 131 are bolted onto the outer edge of flange 71 on the side of the trough in the edge.

portion of the structure. Stops 130 and 131 are provided to restrain rollers 101 and 103 against unlimited upward movement during the removal of anchor bolt 75 from the troughs in which it nests for locking the access door to close the opening. The stops also act with the rollers to efiect a self-locking action when the bolt is in locking position.

Tab 135 on plate 122 provides a means on which to rotation removes rollers 101 and 103 from contact with edge portion 73 of the access door. With the nuts so released from the front of the door, continued upward movement of lever arm 115 results in further rotation of the cams 98 and 99. This rotation of the cams brings pin 129 into contact with the lower wall of anchor bolt 75 so that upon further upward action of lever arm 115 there is a positive movement or lifting of anchor bolt 75 from its nesting position in the troughs in the edge of the door and the access opening. The pivotal movement of anchor bolt 75 about pivot pin 84 raises the bolt in a counterclockwise manner, as shown in FIG. 13, to a position at which it is clear of the troughs in the door and the access opening. By reversing the described operation, anchor bolt 75 can be repositioned into locking arrangement to secure the door tightly in place against the wall surface face of the access opening.

The latching mechanism described is particularly useful for securing access doors in place on vessels and tanks such as used in electric power generation by atomic energy. Such doors require very secure and tight seals and generally require use of many bolts to achieve the desired seal.

Various changes and modifications of the invention can be made and will occur to those skilled in the art;

however, to the extent such variations incorporate the spirit of the invention, they are intended to be encompassed within the scope of the following claims.

What is claimed is:

' l. A latch mechanism comprising:

a locking bolt pivotally mounted to a supporting bracket;

a pivot shaft extending laterally from the side of the bolt between the bolt ends;

a cam mounted on the pivot shaft to rotate relative to the bolt; and

a lever arm pivotally joined to the cam at a point spaced away from the pivot shaft to rotate the cam;

said cam having a contact face which, upon touching a stationary surface, restrains forward movement of the bolt and applies a rearward force thereon.

2, A latch mechanism according to claim 1 having means joined to the lever arm to raise the bolt from a locking position upon rotation of the cam.

3. A latch mechanism according to claim 1 having resilient means communicating with the bolt to urge it into a prelocking position.

4. A latch mechanism according to claim 1 in which the bolt is slidably mounted, as "i'jil as pivotally mounted, to the bracket.

5. A latch mechanism according to claim 4 having resilient means which urges the bolt forward with respect to the bracket.

6. A latch mechanism according to claim 1 in which the cam contact surface upon touching a stop lug on the stationary surface ends pivotal movement of the bolt.

7. A latch mechanism comprising:

a locking bolt pivotally mounted to a supporting bracket;

a pivot shaft extending laterally from the side of the bolt between the bolt ends;

a cam mounted on the pivot shaft to rotate relative to the bolt;

said cam having a contact face which, upon touching a stationary surface, restrains forward movement of the bolt and applies a rearward force thereon;

a lever arm pivotally joined to the cam at a point spaced away from the pivot shaft to rotate the cam; and

a pin mounted on the cam and extending below the bolt to move the bolt from a locking position upon rotation of the cam and displacement of the pin into contact with the bolt.

8. A latch mechanism according to claim 7 having resilient means communicating with the bolt to urge it into a prelocking position.

9. A latch mechanism according to claim 7 in which the bolt is slidably mounted, as well as pivotally mounted, to the bracket.

10. A latch mechanism according to claim 9 having resilient means which urges the bolt forward with respect to the bracket.

11. A latch mechanism according to claim 10 in which the cam has a contact face which, upon touching a stationary surface, restrains forward movement of the bolt.

12. A latch mechanism according to claim 11 in t which the cam contact surface upon touching a stop lug on the stationary surface ends pivotal movement of the bolt.

13. A latch mechanism comprising:.

a locking bolt mounted by a pivot to a supporting bracket;

a pivot shaft rotatably positioned in a hole on the bolt lateral to the bolt axis;

a pair of similar cams fixedly mounted on the pivot shaft with one cam on each side of the bolt; and

a lever arm pivotally joined to one of the cams at a point spaced away from the pivot shaft to simultaneously rotate the cams and pivot shaft in unison;

said cams having contact faces which, upon touching a stationary surface, restrain forward movement of the bolt and apply a rearward force thereon.

14. A latch mechanism according to claim 13 having means joined to the lever arm to raise the bolt upon rotation of the cams.

15. A latch mechanism according to claim 13 in which the bolt is slidably mounted, as well as pivotally mounted, to the bracket, and in which the contact face of each cam is a roller mounted thereon, with the axis of each roller being lateral to the axis of the bolt, said rollers being positioned to be contactable with a stationary surface to restrain forward movement of the bolt.

16. A latch mechanism according to claim 15 having resilient means which urges the bolt forward with respect to the bracket.

17. A latch mechanism comprising:

a locking bolt mounted by a pivot to a supporting bracket;

a pivot shaft rotatably positioned in a hole on the bolt,

a lever arm pivotally joined to one of the cams at a point spaced away from the pivot shaft to simultaneously rotate the cams and pivot shaft in unison; and

a pin mounted on and extending between the cams below the bolt to move the bolt upon rotation of the cams with displacement of the pin into contact with the bolt.

18. in combination:

an enclosed structure having an opening for access thereto;

an access door, which can close the opening, mounted movably to the structure; and a latch mechanism for securing the door'in closed-position over the opening in the structure;

the structure opening and access door each having complementary edge portions with faces which seal and close the opening, said edge portions each having a plurality of similar troughs, a pair of which in aligned and mating position are adapted to receive a locking bolt;

the latch mechanism comprising a locking bolt pivotally mounted to a supporting bracket on the structure to be swung into and out of engagement with a pair of said mating troughs;

a pivot shaft extending laterally from the side of the I bolt between the bolt ends;

a cam mounted on the pivot shaft to rotate relative to the bolt;

said cam having a contact face which, upon touching a stationary surface of the structure, restrains forward movement of the bolt and applies a rearward force thereon;

a lever arm pivotally joined to the cam at a point spaced away from the pivot shaft to rotate the cam; and

a pin mounted on the cam and extending below the bolt to move 'the bolt from the mating troughs upon rotation of the cam and displacement of the pin into contact with the bolt.

19. The combination of claim 17 in which the bolt is slidably mounted, as well as pivotally mounted, to the bracket.

20. In combination:

an enclosed structure having an opening for access thereto; I

an access door, which can close the opening, mounted movably to the structure; and a latch mechanism for securing the door in closed position over the opening in the st: ucture the structure opening and access door each having complementary edge portions with faces which seal and close the opening, said edge portions each having a plurality of similar troughs, a pair of which in aligned and mating position are adapted to receive a locking bolt;

the latch mechanism comprising a locking bolt mounted by a pivot to a supporting bracket on the structure, to be swung into and out of engagement with a pair of said mating troughs;

a pivot shaft rotatably positioned in a hole on the bolt lateral to the bolt axis;

a pair of similar cams fixedly mounted on the pivot shaft with one cam on each side ofthe bolt;

said cams having contact faces which, upon contacting the rear surface of the structure opening edge portion trough, restrain movement of the bolt and apply a rearward force thereon;

a lever arm pivotally joined to one of the cams at a point spaced away from the pivot shaft to simultaneously rotate the cams and pivot shaft in unison; and

a pin mounted on and extending between the cams below the bolt to move the bolt upon rotation of 'the cams with displacement of the pin into contact with the bolt.

21. ln'corn'bination:

an enclosed structure having an opening for access thereto;

an access door, which can close the opening, mounted movably to the structure; and a latch mechanism for securing the door in closed position over the opening in the structure;

the structure opening and access door each having complementary edge portions with faces which seal and close the opening, said edge portions each having a plurality of similar troughs, a pair of which in aligned and mating position are adapted to receive a locking bolt;

the latch mechanism comprising a locking bolt pivotally mounted to a supporting bracket on the structure to be swung into and out of engagement with a pair of said mating troughs;

a pivot shaft extending laterally from the side of the bolt between the bolt ends;

a cam mounted on the pivot shaft to rotate relative to the bolt; and

a lever arm pivotally joined to the cam at a point spaced away from the pivot shaft to rotate the cam;

said cam having a contact face which, upon touching a stationary surface of the structure, restrains forward movement of the bolt and applies a rearward force thereon.

22. The combination of claim 21 including means to lift the bolt from the mating troughs upon rotation of the cam.

23. The combination of claim 21 in which the bolt is slidably mounted, as well as pivotally mounted, to the bracket.

24. In combination:

an enclosed structure having an opening for access thereto;

an access door, which can close the opening,

mounted movably to the structure; and

a latch mechanism for securing the door in closed position over the opening in the structure;

the structure opening and access door each having complementary edge portions with faces which seal and close the opening, said edge portions each having a plurality of similar troughs, a pair of which in aligned and mating position are adapted to receive a locking bolt;

the latch mechanism comprising a locking bolt mounted by a pivot to a supporting bracket on the structure, to be swung into and out of engagement with a pair of said mating troughs;

a pivot shaft rotatably positioned in a hole on the bolt lateral to the bolt axis;

a pair of similar cams fixedly mounted on the pivot shaft with one cam on each side of the bolt;

said cams having contact faces which, upon contacting the rear surface of the structure opening edge portion trough, restrain movement of the bolt and apply a rearward force thereon;

a lever arm pivotally joined to one of the cams at a point spaced away from the pivot shaft to simultaneously rotate the cams and pivot shaft in unison; and

means connected to the cams to raise the bolt upon rotation of the cams.

25. The combination of claim 24 in which the bolt is slidably mounted, as well as pivotally mounted, to the bracket, and in which the contact face of each cam is a roller mounted thereon with the axis of each roller being lateral to the axis of the bolt, said rollers being positioned to contact the rear surface of the structure opening edge portion trough to restrain forward movement of the bolt in the trough.

26. A latch mechanism comprising:

a locking bolt slidably and pivotally mounted to a supporting bracket;

a pivot shaft rotatably positioned in a hole on the bolt lateral to the bolt axis;

a pair of similar cams fixedly mounted on the pivot shaft with one cam on each side ofthe bolt;

a roller mounted to each cam with the axis of each roller being lateral to the axis of the bolt, said rollers being positioned to be contactable with a stationary surface to restrain forward movement of the bolt;

a lever arm joined to one of the cams to simultaneously rotate the cams and pivot shaft in unison; and

a pin mounted on and extending between the cams below the bolt to move the bolt upon rotation of the cams with displacement of the pin into contact with the bolt.

27. A latch mechanism according to claim 26 having resilient means which urges the bolt forward 'with respect to the bracket.

28. In combination:

an enclosed structure having an opening for access thereto;

an access door, which can close the opening, mounted movably to the structure; and a latch mechanism for securing the door in closed position over the opening in the structure;

the structure opening and access door each having complementary edge portions with faces which seal and close the opening, said edge portions each having a plurality of similar troughs, a pair of which in aligned and mating position are adapted to receive a locking bolt;

the latch mechanism comprising a locking bolt slidably and pivotally mounted to a supporting bracket on the structure, to be swung into and out of engagement with a pair of said mating troughs;

a pivot shaft rotatably positioned in a hole on the bolt lateral to the bolt axis;

a pair of similar cams fixedly mounted on the pivot shaft with one cam on each side of the-bolt;

a roller mounted to each cam with the axis of each roller being lateral to the axis of the bolt, said rollers being positioned to contact the rear surface of the structure opening edge portion trough to restrain forward movement of the bolt in the trough;

a lever arm joined to one of the cams to simultaneously rotate the cams and pivot shaft in unison; and

a pin mounted on and extending between the cams below the bolt to move the bolt upon rotation of the cams with displacement of the pin into contact with the bolt. 2

29. The combination of claim 28 in which a spring communicates with the bolt and urges it into the mating troughs. 

1. A latch mechanism comprising: a locking bolt pivotally mounted to a supporting bracket; a pivot shaft extending laterally from the side of the bolt between the bolt ends; a cam mounted on the pivot shaft to rotate relative to the bolt; and a lever arm pivotally joined to the cam at a point spaced away from the pivot shaft to rotate the cam; said cam having a contact face which, upon touching a stationary surface, restrains forward movement of the bolt and applies a rearward force thereon.
 2. A latch mechanism according to claim 1 having means joined to the lever arm to raise the bolt from a locking position upon rotation of the cam.
 3. A latch mechanism according to claim 1 having resilient means communicating with the bolt to urge it into a prelocking position.
 4. A latch mechanism according to claim 1 in which the bolt is slidably mOunted, as well as pivotally mounted, to the bracket.
 5. A latch mechanism according to claim 4 having resilient means which urges the bolt forward with respect to the bracket.
 6. A latch mechanism according to claim 1 in which the cam contact surface upon touching a stop lug on the stationary surface ends pivotal movement of the bolt.
 7. A latch mechanism comprising: a locking bolt pivotally mounted to a supporting bracket; a pivot shaft extending laterally from the side of the bolt between the bolt ends; a cam mounted on the pivot shaft to rotate relative to the bolt; said cam having a contact face which, upon touching a stationary surface, restrains forward movement of the bolt and applies a rearward force thereon; a lever arm pivotally joined to the cam at a point spaced away from the pivot shaft to rotate the cam; and a pin mounted on the cam and extending below the bolt to move the bolt from a locking position upon rotation of the cam and displacement of the pin into contact with the bolt.
 8. A latch mechanism according to claim 7 having resilient means communicating with the bolt to urge it into a prelocking position.
 9. A latch mechanism according to claim 7 in which the bolt is slidably mounted, as well as pivotally mounted, to the bracket.
 10. A latch mechanism according to claim 9 having resilient means which urges the bolt forward with respect to the bracket.
 11. A latch mechanism according to claim 10 in which the cam has a contact face which, upon touching a stationary surface, restrains forward movement of the bolt.
 12. A latch mechanism according to claim 11 in which the cam contact surface upon touching a stop lug on the stationary surface ends pivotal movement of the bolt.
 13. A latch mechanism comprising: a locking bolt mounted by a pivot to a supporting bracket; a pivot shaft rotatably positioned in a hole on the bolt lateral to the bolt axis; a pair of similar cams fixedly mounted on the pivot shaft with one cam on each side of the bolt; and a lever arm pivotally joined to one of the cams at a point spaced away from the pivot shaft to simultaneously rotate the cams and pivot shaft in unison; said cams having contact faces which, upon touching a stationary surface, restrain forward movement of the bolt and apply a rearward force thereon.
 14. A latch mechanism according to claim 13 having means joined to the lever arm to raise the bolt upon rotation of the cams.
 15. A latch mechanism according to claim 13 in which the bolt is slidably mounted, as well as pivotally mounted, to the bracket, and in which the contact face of each cam is a roller mounted thereon, with the axis of each roller being lateral to the axis of the bolt, said rollers being positioned to be contactable with a stationary surface to restrain forward movement of the bolt.
 16. A latch mechanism according to claim 15 having resilient means which urges the bolt forward with respect to the bracket.
 17. A latch mechanism comprising: a locking bolt mounted by a pivot to a supporting bracket; a pivot shaft rotatably positioned in a hole on the bolt lateral to the bolt axis; a pair of similar cams fixedly mounted on the pivot shaft with one cam on each side of the bolt; said cams having contact faces which, upon touching a stationary surface, restrain forward movement of the bolt and apply a rearward force thereon; a lever arm pivotally joined to one of the cams at a point spaced away from the pivot shaft to simultaneously rotate the cams and pivot shaft in unison; and a pin mounted on and extending between the cams below the bolt to move the bolt upon rotation of the cams with displacement of the pin into contact with the bolt.
 18. In combination: an enclosed structure having an opening for access thereto; an access door, which can close the opening, mounted movably to the structure; and a latch mechanism for securing the door in closed position over the opening in the structure; the structure opening and access door each having complementary edge portions with faces which seal and close the opening, said edge portions each having a plurality of similar troughs, a pair of which in aligned and mating position are adapted to receive a locking bolt; the latch mechanism comprising a locking bolt pivotally mounted to a supporting bracket on the structure to be swung into and out of engagement with a pair of said mating troughs; a pivot shaft extending laterally from the side of the bolt between the bolt ends; a cam mounted on the pivot shaft to rotate relative to the bolt; said cam having a contact face which, upon touching a stationary surface of the structure, restrains forward movement of the bolt and applies a rearward force thereon; a lever arm pivotally joined to the cam at a point spaced away from the pivot shaft to rotate the cam; and a pin mounted on the cam and extending below the bolt to move the bolt from the mating troughs upon rotation of the cam and displacement of the pin into contact with the bolt.
 19. The combination of claim 17 in which the bolt is slidably mounted, as well as pivotally mounted, to the bracket.
 20. In combination: an enclosed structure having an opening for access thereto; an access door, which can close the opening, mounted movably to the structure; and a latch mechanism for securing the door in closed position over the opening in the structure; the structure opening and access door each having complementary edge portions with faces which seal and close the opening, said edge portions each having a plurality of similar troughs, a pair of which in aligned and mating position are adapted to receive a locking bolt; the latch mechanism comprising a locking bolt mounted by a pivot to a supporting bracket on the structure, to be swung into and out of engagement with a pair of said mating troughs; a pivot shaft rotatably positioned in a hole on the bolt lateral to the bolt axis; a pair of similar cams fixedly mounted on the pivot shaft with one cam on each side of the bolt; said cams having contact faces which, upon contacting the rear surface of the structure opening edge portion trough, restrain movement of the bolt and apply a rearward force thereon; a lever arm pivotally joined to one of the cams at a point spaced away from the pivot shaft to simultaneously rotate the cams and pivot shaft in unison; and a pin mounted on and extending between the cams below the bolt to move the bolt upon rotation of the cams with displacement of the pin into contact with the bolt.
 21. In combination: an enclosed structure having an opening for access thereto; an access door, which can close the opening, mounted movably to the structure; and a latch mechanism for securing the door in closed position over the opening in the structure; the structure opening and access door each having complementary edge portions with faces which seal and close the opening, said edge portions each having a plurality of similar troughs, a pair of which in aligned and mating position are adapted to receive a locking bolt; the latch mechanism comprising a locking bolt pivotally mounted to a supporting bracket on the structure to be swung into and out of engagement with a pair of said mating troughs; a pivot shaft extending laterally from the side of the bolt between the bolt ends; a cam mounted on the pivot shaft to rotate relative to the bolt; and a lever arm pivotally joined to the cam at a point spaced away from the pivot shaft to rotate the cam; said cam having a contact face which, upon touching a stationary surface of the structure, restrains forward movement of the bolt and applies a rearward force thereon.
 22. The combination of claim 21 including means to lift the bolt from the mating troughs upon rotation of the cam.
 23. The combination of claim 21 in which the bolt is slidably mounted, as well as pivoTally mounted, to the bracket.
 24. In combination: an enclosed structure having an opening for access thereto; an access door, which can close the opening, mounted movably to the structure; and a latch mechanism for securing the door in closed position over the opening in the structure; the structure opening and access door each having complementary edge portions with faces which seal and close the opening, said edge portions each having a plurality of similar troughs, a pair of which in aligned and mating position are adapted to receive a locking bolt; the latch mechanism comprising a locking bolt mounted by a pivot to a supporting bracket on the structure, to be swung into and out of engagement with a pair of said mating troughs; a pivot shaft rotatably positioned in a hole on the bolt lateral to the bolt axis; a pair of similar cams fixedly mounted on the pivot shaft with one cam on each side of the bolt; said cams having contact faces which, upon contacting the rear surface of the structure opening edge portion trough, restrain movement of the bolt and apply a rearward force thereon; a lever arm pivotally joined to one of the cams at a point spaced away from the pivot shaft to simultaneously rotate the cams and pivot shaft in unison; and means connected to the cams to raise the bolt upon rotation of the cams.
 25. The combination of claim 24 in which the bolt is slidably mounted, as well as pivotally mounted, to the bracket, and in which the contact face of each cam is a roller mounted thereon with the axis of each roller being lateral to the axis of the bolt, said rollers being positioned to contact the rear surface of the structure opening edge portion trough to restrain forward movement of the bolt in the trough.
 26. A latch mechanism comprising: a locking bolt slidably and pivotally mounted to a supporting bracket; a pivot shaft rotatably positioned in a hole on the bolt lateral to the bolt axis; a pair of similar cams fixedly mounted on the pivot shaft with one cam on each side of the bolt; a roller mounted to each cam with the axis of each roller being lateral to the axis of the bolt, said rollers being positioned to be contactable with a stationary surface to restrain forward movement of the bolt; a lever arm joined to one of the cams to simultaneously rotate the cams and pivot shaft in unison; and a pin mounted on and extending between the cams below the bolt to move the bolt upon rotation of the cams with displacement of the pin into contact with the bolt.
 27. A latch mechanism according to claim 26 having resilient means which urges the bolt forward with respect to the bracket.
 28. In combination: an enclosed structure having an opening for access thereto; an access door, which can close the opening, mounted movably to the structure; and a latch mechanism for securing the door in closed position over the opening in the structure; the structure opening and access door each having complementary edge portions with faces which seal and close the opening, said edge portions each having a plurality of similar troughs, a pair of which in aligned and mating position are adapted to receive a locking bolt; the latch mechanism comprising a locking bolt slidably and pivotally mounted to a supporting bracket on the structure, to be swung into and out of engagement with a pair of said mating troughs; a pivot shaft rotatably positioned in a hole on the bolt lateral to the bolt axis; a pair of similar cams fixedly mounted on the pivot shaft with one cam on each side of the bolt; a roller mounted to each cam with the axis of each roller being lateral to the axis of the bolt, said rollers being positioned to contact the rear surface of the structure opening edge portion trough to restrain forward movement of the bolt in the trough; a lever arm joined to one of the cams to simultaneously rotate the cams and pivot shaft in unison; and a pin mouNted on and extending between the cams below the bolt to move the bolt upon rotation of the cams with displacement of the pin into contact with the bolt.
 29. The combination of claim 28 in which a spring communicates with the bolt and urges it into the mating troughs. 